It has been determined that it may be desirable under some conditions to automatically start and stop an engine of a vehicle. By automatically stopping an engine, it may be possible to reduce fuel consumption for a vehicle. For example, an engine may be stopped when a vehicle is at a stop light and forward motion is not desired. In this way, fuel consumption by the engine may cease for several minutes, thereby reducing fuel consumption. The engine may be restarted in response to a change in brake pedal state or an increase in driver demand torque. However, if the engine starts too lean or too rich after engine stopping, engine emissions may degrade such that the benefit of reduced fuel consumption is over shadowed by the increase in engine emissions.
The inventors herein have recognized the above-mentioned disadvantages and have developed a method for starting an engine, comprising: stopping the engine; and adjusting an amount of fuel supplied to a cylinder in response to engine stop position, the amount of fuel participating in a first combustion event since engine stop.
By adjusting an amount of fuel injected to a cylinder intake port in response to engine stop position, the amount of fuel participating in a first combustion event in the engine since engine stop, it may be possible to improve engine air-fuel control during engine starting. In particular, the engine stop position may provide an indication, or an ability to infer, an amount of injected fuel that will enter a cylinder via an intake port during engine starting. If engine position indicates less than the injected fuel amount is expected to enter the cylinder, the amount of fuel injected may be increased so that a desired amount of fuel enters the cylinder. In this way, it may be possible to provide more consistent engine air-fuel ratio control during engine starting.
The present description may provide several advantages. Specifically, the approach may improve engine starting consistency by reducing the possibility of engine misfire. In addition, the approach may improve engine starting emissions by providing more accurate air-fuel control. Further, the approach may improve engine run-up speed control by providing more repeatable engine torque during engine run-up to idle speed.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.